package com.zkw.adt.list;

import java.util.Iterator;
import java.util.NoSuchElementException;

/**
 * Created by Administrator on 2016/5/28 0028.
 * 自己实现ArrayList
 */
public class MyArrayList<AnyType> implements Iterable<AnyType> {
    private static final int DEFAULT_CAPACITY=10;

    private int theSize;
    private AnyType[] theItems;

    public MyArrayList() {
        clear();
    }

    public void clear(){
        theSize=0;
        ensureCapacity(DEFAULT_CAPACITY);
    }

    public int size(){
        return theSize;
    }

    public boolean isEmpty(){
        return size()==0;
    }

    public void trimToSize(){
        ensureCapacity(size());
    }

    public AnyType get(int idx){
        if (idx<0||idx>size())
            throw new ArrayIndexOutOfBoundsException();
        return theItems[idx];
    }

    public AnyType set(int idx,AnyType newVal){
        if (idx<0||idx>size())
            throw new ArrayIndexOutOfBoundsException();
        AnyType old=theItems[idx];
        theItems[idx]=newVal;
        return old;
    }

    public void ensureCapacity(int newCapacity){
        if (newCapacity<theSize)
            return;
        AnyType[] old=theItems;
        theItems=(AnyType[]) new Object[newCapacity];
        for (int i=0;i<size();i++)
            theItems[i]=old[i];
    }

    public boolean add(AnyType x){
        add(size(),x);
        return true;
    }

    public void add(int idx,AnyType x){
        if (theItems.length==size())
            ensureCapacity(size()*2+1);
        for (int i=theSize;i>idx;i--)
            theItems[i]=theItems[i-1];
        theItems[idx]=x;
        theSize++;
    }

    public AnyType remove(int idx){
        AnyType removedItem=theItems[idx];
        for (int i=idx;i<size()-1;i++)
            theItems[i]=theItems[i+1];
        theSize--;
        return removedItem;
    }

    public Iterator iterator() {
        return new ArrayListIterator();
    }

    private class ArrayListIterator implements Iterator<AnyType>{
        private int current=0;

        @Override
        public boolean hasNext() {
            return current<size();
        }

        @Override
        public AnyType next() {
            if (!hasNext())
                throw new NoSuchElementException();
            return theItems[current++];
        }

        public void remove(){
            MyArrayList.this.remove(--current);
        }
    }
}
